This is a clinical study of the efficacy of regional radiation therapy in the treatment of patients with carcinoma of the prostate. A recent review of the long-term results in the treatment of 310 consecutive patients, treated with external beam megavoltage radiation limited to the region of the prostate gland, demonstrated 5 and 10-year actuarial survival rates of 72% and 48%, respectively, in patients with disease limited by the prostatic capsule, and 48% and 27%, respectively, in patients with extracapsular extension. A reasonable explanation for this significant difference in survival rests on the hypothesis that once the primary neoplasm has extended beyond the prostatic capsule, regional lymph node involvement is likely. In this study, the precise degree of involvement will be determined by appropriate diagnostic studies and surgical staging prior to the selection of the treatment technique. Patients will be treated who have (a) prostatic involvement only, (b) prostatic involvement plus pelvic lymph node involvement, and (c) prostatic involvement plus pelvic lymph node involvement plus para- aortic lymph node involvement. Patients with other metastatic sites will be excluded. In all patients the proven sites of involvement will be treated. In one-half of the patients assigned by random allocation, radiotherapy will be extended to include the next most proximal uninvolved lymph node group. In addition, all patients will be carefully observed in order to assess the tempo of dissemination and the influence upon survival of reasonable palliative measures, such as hormone manipulation in those in whom the primary radiation treatment is unsuccessful.